Question: Solve for $x$ and $y$ using substitution. ${-2x+2y = 6}$ ${y = 2x+4}$
Explanation: Since $y$ has already been solved for, substitute $2x+4$ for $y$ in the first equation. ${-2x + 2}{(2x+4)}{= 6}$ Simplify and solve for $x$ $-2x+4x + 8 = 6$ $2x+8 = 6$ $2x+8{-8} = 6{-8}$ $2x = -2$ $\dfrac{2x}{{2}} = \dfrac{-2}{{2}}$ ${x = -1}$ Now that you know ${x = -1}$ , plug it back into $\thinspace {y = 2x+4}\thinspace$ to find $y$ ${y = 2}{(-1)}{ + 4}$ $y = -2 + 4$ $y = 2$ You can also plug ${x = -1}$ into $\thinspace {-2x+2y = 6}\thinspace$ and get the same answer for $y$ : ${-2}{(-1)}{ + 2y = 6}$ ${y = 2}$